Marine reheater cycle



May 23, 1967 D. TAWSE 3,32

' MARINE REHEATER CYCLE Filed June 17, 1965 cor v oe/vs INVENTOR DAV/D TAWSE AT TORNEY United States Patent 3,320,752 MARHNE REHEATER YLE David Tawse, Thompsonville, Conn., assignor to Combustion Engineering, 1110., Windsor, Conn., 21 corporation of Delaware Filed June 17, 1965, Ser. No. 464,787 12 Claims. (Cl. 60-192) The present invention relates to marine power plant installations and their method of operation. More particularly, the invention relates to a marine power plant installation including separate turbines operable for ahead and astern operation and wherein the ahead turbine op erates on a reheat steam cycle.

Problems arise with the application of a reheat cycle to marine power plants due to the fact that turbines are required to operate a vessel both in the ahead direction and in the astern direction. The need for a separate turbine to operate the vessel in the astern direction creates much difiiculty and in most cases even prevents the use of a reheater due to the fact that when steam flow to the astern turbine is commenced the supply to the ahead turbine must be discontinued and this in turn means that steam flow to the reheater is also discontinued thereby starving the reheater tubes of cooling fluid. With no cooling fluid flowing through the reheater the tubes are subject to deterioration by burnout. Therefore, it has been the practice when employing reheaters in such installations either to locate them in a low temperature region of the steam generator such as in the gas pass behind the boiler bank or to employ independently heated heat exchangers such as separately fired reheaters or those in which line steam is employed as a heating medium.

The location of a tubular reheater in the gas pass is undesirable due to the fact that the presence of relatively low gas temperatures requires an excessive amount of heating surface in the reheater therefore necessitating a reheater of tremendous proportions that is high in initial cost and low in operational efiiciency. The latter two of the above methods of reheat are also undesirable in that they require duplication of feed and firing controls and other ancillary equipment necessary for the operation of a reheater separate from the main steam generator.

By means of the present invention there is provided a marine power plant installation wherein the ahead turbine is operated on a reheat steam cycle and in which the reheater is permitted to be located in a high temperature region of the steam generator thereby increasing the overall efiiciency of the steam cycle and reducing the initial cost of manufacturing the reheat equipment. In general terms, the invention provides for a marine power plant installation including a multi-stage ahead turbine and an astern turbine both of which are supplied with steam from a steam generator including an evaporator section, a superheater and a reheater located in a high gas temperature region of the steam generator. The installation also includes a desuperheater located in the system between the superheater and the inlet to the astern turbine such that steam supplied by the superheater to the astern turbine is first reduced in temperature in the desuperheater and then raised to the desired turbine temperature in the reheater thereby permitting full steam flow through the reheater during operation of the astern turbine.

The objects and the attendant advantages of the instant invention will become apparent when considered in connection with the accompanying description including the drawings of which:

The single figure is a schematic representation of a marine power plant installation employing the invention.

Referring now to the figure there is shown a marine power plant installation including a steam generator 3,320,752 Patented May 23, 1967 and a turbine 12 operable for ahead operation of the vessel and a turbine 14 operable for astern operation thereof. The vapor generator 10 comprises a furnace chamber 16 and a boiler bank 18 including upper drum 20, lower drum 22 and a bank of interconnecting tubes 24. Interposed between the furnace section 16 and the boiler bank 18 are a superheater 26 and a reheater 28 in open gaseous communication with both the furnace chamber 16 and the boiler bank 18. The ahead turbine 12 is of the multistage type including a high pressure section 30 and a low pressure section 32. However, it is to be understood that the number of stages in the turbine employed can be increased Without departing from the spirit of the invention. A plurality of steam conduits connect the steam generator equipment to the turbines 12 and 14 for their operation on a reheat cycle. These conduits include steam line 34 connecting the outlet of the superheater 26 to the inlet of the high pressure stage 30 of the ahead turbine 12, line 36 connecting the exhaust of the high pressure stage 30 to the inlet of the reheater 28 and line 38 connecting the reheater outlet to the inlet of the low pressure stage 32 of the turbine 12. The steam lines 34, 36 and 38 are equipped with valves 40, 42 and 44 that are operable to admit or discontinue flow of steam to the turbine 12. In order to pass steam from the vapor generator 10 to the astern turbine 14 there is provided a steam line 46 that connects between the line 38 between the outlet of the reheater 28 and the valve 44 and the inlet to the astern turbine 14. Valve 47 is located in line 46 to control the flow of steam to the astern turbine 14.

According to the invention a desuperheater 48, shown in FIGURE 1 as being of the indirect type, is submerged below the water level in the upper drum 20. The de superheater 48 may be located in other water containing parts of the steam generator such as the lower drum 22 without departing from the spirit of the invention. It is connected in the system by inlet and outlet lines 50 and 52, respectively, that connect the desuperheater between the steam line 36 intermediate the valve 42 and the inlet of the reheater 28 and the line 34 intermediate the valve 40 and the inlet of superheater 26 such that, when desired, steam can be caused to flow from the superheater, through the desuperheater and thence through the reheater. A valve 54 is provided in the desuperheater discharge line 52 for placing the desuperheater 48 either in or out of service.

Control means here shown as being a simple bar linkage 56 are employed to operate the valves 40, 42, 44, 47 and 54. The arrangement is such that the valves 40, 42 and 44 that control the supply of steam to the ahead turbine 12 are arranged to operate in unison as are the valves 47 and 54 that etfect the supply of steam to the astern turbine 14. The arrangement shown is such that actuation of the valves 40, 42 and '44 to an open position at the same time closes valves 47 and 54 and vice versa. The control means 56 can embody any means for controlling the operation of the valves in the system such as means that are electrically, pneumatically or hydraulically actuated. In the alternative, the two groups of valves, 40, 42, 44 and valves 47, 54 can be arranged to operate in unison with the valves of the same group but independently of those of the other group without departing from the spirit of the invention.

The operation of the herein described power plant installation is as follows. Fuel and water are admitted to the vapor generator 10 wherein combustion of the fuel in the furnace section 16 effects a transfer of heat from the combustion gases through the water contained in the pressure parts of the vapor generator wherein saturated steam is created and collected in the upper drum 20. The saturated steam is passed to the superheater 26 where it is increased to about 1000 F. When it is desired to "ice perate the vessel in the ahead direction the control neans 56 are actuated to open the valves 40, 42 and 44 hat admit steam to the ahead turbine 12 and to close he valves 47 and 54 thereby to bypass the desuperheater -8 and the astern turbine 14. Superheater steam is then aermitted to pass from the outlet of the superheater 26 hrough line 34 to the inlet of the high pressure stage of the turbine 12. The exhaust steam from the high nressure stage then passes through line 36 to the reheater vhere its temperature is raised to 1000 F. This lower )ICSS'UI'C steam then passes through line 38 to the inlet f the low pressure stage 32 of the turbine 12 and then 0 a condenser (notshown).

When it is desired to. operate the vessel in the astern lire-ction flow of steam to the ahead turbine 12 is dis- :ontinuedpby the control means 56 closing the valves i0, 42 and 44 and admitted to the astern turbine 14 by )pening the valves 47 and 54. In this manner steam :merging from the outlet of the superheater 26 at 1000" F. is caused to flow through the desuperheater inlet line 50 to the desuperheater 48 where the temperature is re- :luced to about 700 F. and thence through the desuperheater outlet line 52. to the reheater 28 where its temperature is raised to 1000 F. From the reheater the steam passes through line 46 to the inlet of the turbine 14. Exhaust steam from the turbine 14 is passed to a condenser (not shown).

By means of the present invention there is provided a simple and effective means for permitting the use of a conventional reheater, located in a high gas section of a steam generator. The invention permits the full flow of steam through the reheater during astern operation of the vessel thereby enabling the reheater to be cooled at all times during the operation of the steam generator. By locating the reheater in a high gas temperature section of the steam generator the size of its heat exchange surface is kept to a minimum thereby lowering the initial cost of the equipment and the heat transfer efiiciency is raised to a maximum thereby increasing the over-all efliciency of the steam cycle.

It will be understood that various changes in thedetails, materials, and arrangements of parts which have been herein described and illustrated in orderto explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. For example, while the disclosed arrangement embodies a desuperheater of the indirect type it should be understood that. a spray type desuperheater could be employed without departingfrom the spirit of the claims- What is claimed is:

1. A method of operating a marine power plant installation comprising a two-stage ahead turbine, an astern turbine, a steam generator including a superheater, a desuperheater and a reheater, the steps comprising sequentially flowing steam from said superheater to the first stage of said ahead turbine, to the reheater and to the second stage of said ahead turbine during ahead operation of said power plant installation; discontinuing steam flow to said ahead turbine and sequentially flowing steam from said superheater to said desuperheater, to said reheater to said astern turbine during astern operation of said power plant installation.

2. A method of operating a marine power plant installation comprising a two-stage ahead turbine, an astern turbine, a steam generator including a superheater, a desuperheater and a reheater, the steps comprising flowing steam from said superheater in direct sequence to the first stage of said ahead turbine, to said reheater and to the second stage of said ahead turbine in bypass relation to said desuperheater and said astern turbine during ahead operation of said power plant installation; flowing steam from said superheater in direct sequence tovsaid desuperheater, to said reheater and to said astern turbine in bypass relation to said ahead turbine during astern operation of said power plant installation.

3. A marine power plant installation comprising a multistage ahead turbine; an astern turbine; a steam generator including an evaporator section, a superheater, a desuperheater, and a reheater; means operable to connect said evaporator section, said superheater, said ahead turbine and said reheater for series steam flow and to bypass .said desuperheater and said astern turbine during ahead operation of said power plant installation; means operable to connect said evaporator section, said superheater, said desuperheater, said reheater and said astern turbine for series steam flow and to bypass said ahead turbine dursecond valve means to a closed position for ahead operation of said power plant installation; and means for actuating said first valve means to a closed position and said second valve means to an open position for astern operation of said power plant installation.

5. A marine power plant installation comprising a twostage ahead turbine; an astern turbine; a steam generator including an evaporator section, a superheater, a desuperheater and a reheater; first conduit means connecting said superheater and the firststage of said ahead turbine; at first valve in said first conduit means; second conduit means for passing exhaust steam from said first stage to said reheater; a second valve in said second conduit means; third conduit means for passing steam from said reheater to said second stage of said ahead turbine; a third valve in said third conduit means; fourth conduit means including a desuperheater connecting said first conduit means upstream of said first valve with said second conduit means downstream of said second valve; a

fourth valve in said fourth conduit means; fifth conduit.

means for passing steam from said reheater to said astern turbine; a fifth valve in said fifth conduit means; control means including means for openingsaid first, second and third valves and closing said fourth and fifth valves for ahead operation of said power plant installation, and means for closing said first, second and third valves and opening said fourth and fifth valves for astern operation of said power plant installation.

6. The organization of claim 5 wherein said desuperheater comprises indirect heat exchange means submerged in a water section of said steam generator.

7. A marine power plant installation comprising a twostage ahead turbine; an astern turbine; a steam generator including a furnace chamber, an evaporator section comprising an upper drum, a lower drum and a bank of interconnecting tubes, a superheater disposed between said furnace chamber and said tube bank, a desuperheater, a reheater disposed between said superheater and said tube bank; first conduit means connecting said superheater and the first stage of said ahead turbine; a first valve in said first conduit means; second conduit means for passing exhaust steam from said first stage to said reheater; a second valve in said second conduit means; third conduit means for passing steam from said reheater to said second stage of said ahead turbine; a third valve in said third conduit means; fourth conduit means including a desuperheater connecting said first conduit means upstream of said first valve with said second conduit means downstream of said second valve; a fourth valve in said fourth conduit means; fifth conduit means for passing steam from said reheater to said astern turbine; a fifth valve in said fifth conduit means; control means including means for opening said first, second and third valves and closing said fourth and fifth valves for ahead operation of said power plant installation, and :means for closing said first, second and third valves and opening said fourth and fifth valves for astern operation of said power plant installation.

8. The organization of claim '7 wherein said desuperheater comprises indirect heat exchange means submerged in a water section of said steam generator.

9. The organization of claim 8 wherein said desuperheater comprises indirect heat exchange means submerged in a water section of said upper drum.

1 A marine power plant installation comprising a two-stage ahead turbine; an astern turbine; a steam generator including a furnace chamber, an evaporator section comprising an upper drum, a lower drum and a bank of interconnecting tubes, a superheater and a reheater located intermediate said furnace chamber and said tube bank and a desuperheater; first conduit means connecting said superheater and the first stage of said ahead turbine; a first valve in said first conduit means; second conduit means for passing exhaust steam from said first stage to said reheater, a second valve in said second conduit means; third conduit means for passing steam from said reheater to said second stage of said ahead turbine; at third valve in said third conduit means; fourth conduit means including a desuperheater connecting said first conduit means upstream of said first valve with said sec ond conduit means downstream of said second valve; 2 fourth valve in said fourth conduit means; fifth conduit means for passing steam from said reheater to said astern turbine; a fifth valve in said fifth conduit means; control means including means for opening said first, second and third valves and closing said fourth and fifth valves for ahead operation of said power plant installation, and means for closing said first, second and third valves and opening said fourth and fifth valves for astern operation of said power plant installation.

11. The organization of claim 16 wherein said desuperheater comprises indirect heat exchange means submerged in a water section of said steam generator.

12. The organization of claim 11 wherein said desuperheater comprises indirect heat exchange means submerged in a water section of said upper drum.

References Cited by the Examiner UNITED STATES PATENTS 2,431,177 11/1947 lager et al. 122-35 2,855,756 10/1958 Hayden et a1. a- 60102 MARTIN P. SCHWADRON, Primary Examiner. R. R. BUNEVICH, Assistant Examiner. 

1. A METHOD OF OPERATING A MARINE POWER PLANT INSTALLATION COMPRISING A TWO-STAGE AHEAD TURBINE, AN ASTERN TURBINE, A STEAM GENERATOR INCLUDING A SUPERHEATER, A DESUPERHEATER AND A REHEATER, THE STEPS COMPRISING SEQUENTIALLY FLOWING STEAM FROM SAID SUPERHEATER TO THE FIRST STAGE OF SAID AHEAD TURBINE, TO THE REHEATER AND TO THE SECOND STAGE OF SAID AHEAD TURBINE DURING AHEAD OPERATION OF SAID POWER PLANT INSTALLATION; DISCONTINUING STEAM FLOW TO SAID AHEAD TURBINE AND SEQUENTIALLY FLOWING STEAM FROM SAID SUPERHEATER TO SAID DESUPERHEATER, TO SAID REHEATER TO SAID ASTERN TURBINE DURING ASTERN OPERATION OF SAID POWER PLANT INSTALLATION. 